Caryopsis

In botany, a caryopsis is a kind of simple dry fruit — one that is monocarpelate (formed from a single carpel) and indehiscent (not opening at maturity) and resembles an achene, apart from that in a caryopsis the pericarp is fused with the thin seed coat.

The caryopsis is commonly called a grain and is the fruit typical of the family Poaceae (or Gramineae), like wheat, rice, and corn. The term grain is as well used in a more general sense as synonymous with cereal (as in "cereal grains", which contain some non-Gramineae). Considering that the fruit wall and the seed are closely fused into a single unit, and the caryopsis or grain is a dry fruit, little concern is given to exactly separating the terms "fruit" and "seed" in these plant structures. In many grains, the "hulls" to be separated prior to processing are actually flower bracts.